[Reuters] Pope John Paul II has told the Archbishop of Canterbury the ordination of women priests in some Anglican churches poses an “increasingly serious obstacle” to progress toward eventual reunion with Rome, the Vatican said Monday.

The Vatican released an exchange of letters between the Pope and Archbishop Robert Runcie, and between Runcie and Johannes Cardinal Willebrands, head of the Vatican’s Secretariat for Christian Unity.

In a letter to Runcie in December, 1984, the Pope said the Roman Catholic Church would continue to adhere to a ban on women priests and that the ordination of Anglican women was a threat to reconciliation between the churches, which split in 1536.

Joint Roman Catholic-Anglican commissions have been discussing the possibility of unity since 1970.

“The increase in the number of Anglican churches which admit, or are preparing to admit, women to priestly ordination constitutes, in the eyes of the Catholic Church, an increasingly serious obstacle to that progress,” the Pope wrote to Runcie.

Anglican churches in Canada, New Zealand, Uganda and Hong Kong have ordained women. The Church of England, which is divided over women priests, will discuss the issue at a general synod in York this week.

In his response nearly a year later, after conferring with Anglican leaders around the world, Runcie acknowledged that the question of women’s ordination had divided Anglicans.

Runcie told the Pope those Anglican communities which have admitted women to the priesthood “have done so for serious doctrinal reason.”

Runcie said there was an urgent need for a joint study of the question of the ordination of women to the priesthood, especially with respect to its consequences on efforts toward eventual Anglican-Roman Catholic unity.

The Pope and Runcie have met three times, including an encounter in Canterbury in 1982 while the Pope was visiting Britain.

Meanwhile, Pope John Paul begins a week-long pastoral visit to Colombia Tuesday. The visit marks the pontiff’s 30th trip abroad and his 7th to Latin America.